For the kraut sauce, peel and finely chop the onion. Heat the oil in a saucepan and let the onions become translucent, dust with flour and roast until light.
Then pour in beef broth. Add salt, pepper and horseradish and let everything boil through. Season to taste with lemon juice and sugar. Finally, add the whipped cream.
For example, the Krensauce goes very well with beef.